Pharmacokinetics of isavuconazole at different target sites in healthy volunteers after single and multiple intravenous infusions.

BACKGROUND: Invasive aspergillosis is a severe fungal infection that affects multiple organ systems including the CNS and the lungs. Isavuconazole, a novel triazole antifungal agent, has demonstrated promising activity against Aspergillus spp. However, data on the penetration of isavuconazole into the CNS and ELF and intracellular accumulation remain limited. MATERIALS AND METHODS: We conducted a prospective single-centre pharmacokinetic (PK) study in 12 healthy volunteers. Subjects received seven doses of 200 mg isavuconazole to achieve an assumed steady-state. After the first and final infusion, plasma sampling was conducted over 8 and 12 h, respectively. All subjects underwent one lumbar puncture and bronchoalveolar lavage, at either 2, 6 or 12 h post-infusion of the final dose. PBMCs were collected in six subjects from blood to determine intracellular isavuconazole concentrations at 6, 8 or 12 h. The AUC/MIC was calculated for an MIC value of 1 mg/L, which marks the EUCAST susceptibility breakpoint for Aspergillus fumigatus and Aspergillus flavus. RESULTS: C max and AUC0-24h of isavuconazole in plasma under assumed steady-state conditions were 6.57 ±â€Š1.68 mg/L (mean ±â€ŠSD) and 106 ±â€Š32.1 h·mg/L, respectively. The average concentrations measured in CSF, ELF and in PBMCs were 0.07 ±â€Š0.03, 0.94 ±â€Š0.46 and 27.1 ±â€Š17.8 mg/L, respectively. The AUC/MIC in plasma, CSF, ELF and in PBMCs under steady-state conditions were 106 ±â€Š32.1, 1.68 ±â€Š0.72, 22.6 ±â€Š11.0 and 650 ±â€Š426 mg·h/L, respectively. CONCLUSION: Isavuconazole demonstrated moderate penetration into ELF, low penetrability into CSF and high accumulation in PBMCs. Current dosing regimens resulted in sufficient plasma exposure in all subjects to treat isolates with MICs ≤ 1 mg/L.

Recombinant human diamine oxidase prevents hemodynamic effects of continuous histamine infusion in guinea pigs.

OBJECTIVE: To test whether recombinant human diamine oxidase (rhDAO) with a mutated heparin-binding motif (mHBM), which shows an increased alpha-distribution half-life, prevents histamine-induced hemodynamic effects. MATERIAL: Thirty-eight female guinea pigs were either pretreated with rhDOA_mHBM or buffer. TREATMENT AND METHODS: Guinea pigs received a continuous infusion of histamine. Heart rate (HR), body core temperature and mean arterial pressure (MAP) were measured and blood was collected. RESULTS: Continuous intravenous infusion of 8 µg/kg/min histamine increased mean peak plasma histamine levels from 5 (± 0.3 SEM) to 28 ng/mL (± 4.9 SEM) after 30 min but had no effect on oxygen saturation. Guinea pigs pretreated with 4 mg/kg rhDAO_mHBM showed lower mean HR (p = 0.008), histamine plasma concentrations (p = 0.002), and higher body core temperatures at the end of the histamine challenge (p = 0.02) compared to controls. Cessation of histamine infusion led to a rebound increase in MAP, but this hemodynamic instability was prevented by rhDAO_mHBM. Pretreatment with 4 mg/kg rhDAO_mHBM reduced urinary histamine (p = 0.004) and 1-Methylhistamine (p < 0.0001) concentrations compared to controls. CONCLUSIONS: Prophylactic infusion of rhDAO_mHBM prevents hemodynamic effects in a guinea pig model of continuous histamine infusion. These findings might help in the translation from animals to humans and in the selection of the optimal dosing of rhDAO_mHBM during human histamine challenge studies.

Switching From Cangrelor to Prasugrel in Patients Undergoing Percutaneous Coronary Intervention: The Switching Antiplatelet-6 (SWAP-6) Study.

BACKGROUND: A drug-drug interaction (DDI) may occur when transitioning from intravenous P2Y12 inhibition with cangrelor to oral P2Y12 inhibition with prasugrel. However, this has never been tested in patients undergoing percutaneous coronary intervention (PCI). OBJECTIVES: This study sought to rule out a DDI when cangrelor and prasugrel are concomitantly administered in PCI patients. METHODS: SWAP-6 (Switching Antiplatelet-6) was a prospective, randomized, 3-arm, open-label pharmacokinetic (PK) and pharmacodynamic (PD) study. Patients (N = 77) were randomized to 1) prasugrel only at the start of PCI, 2) cangrelor plus prasugrel concomitantly at the start of PCI, or 3) cangrelor at the start of PCI plus prasugrel at the end of infusion. Cangrelor infusion was maintained for 2 hours. PK/PD assessments were performed at baseline and 6 time points postrandomization. The primary endpoint was noninferiority in VerifyNow (Werfen) P2Y12 reaction units measured at 4 hours after randomization between cangrelor plus prasugrel concomitantly administered vs prasugrel only. PK assessments included plasma levels of the active metabolite of prasugrel. RESULTS: Compared with prasugrel, cangrelor further enhances P2Y12 inhibitory effects. At 4 hours postrandomization, P2Y12 reaction unit levels were significantly lower with prasugrel only compared to cangrelor and prasugrel concomitantly administered (least squares means difference = 130; 95% CI: 85-176), failing to meet the prespecified noninferiority margin. Findings were corroborated by multiple PD assays. The active metabolite of prasugrel levels were not affected by concomitant administration of cangrelor and were low at the end of cangrelor infusion. CONCLUSIONS: In patients undergoing PCI, concomitant administration of prasugrel with cangrelor leads to a marked increase in platelet reactivity after stopping cangrelor infusion, supporting the presence of a DDI. (Switching Antiplatelet Therapy-6 [SWAP-6]; NCT04668144).

Plasma and intraperitoneal pharmacokinetics of ceftazidime/avibactam in peritoneal dialysis patients.

OBJECTIVES: Peritonitis is a serious complication in patients undergoing automated peritoneal dialysis (APD) that increases morbidity and frequently disqualifies patients from the peritoneal dialysis programme. Ceftazidime/avibactam (CAZ/AVI) is a potential treatment option for APD patients with peritonitis caused by resistant Gram-negative bacteria, but limited data exist on systemic and target-site pharmacokinetics (PK) in patients undergoing APD. This study set out to investigate the PK of CAZ/AVI in plasma and peritoneal dialysate (PDS) of patients undergoing APD. METHODS: A prospective, open-label PK study was conducted on eight patients undergoing APD. CAZ/AVI was administered as a single intravenous dose of 2 g/0.5 g over 120 minutes. APD cycles were initiated 15 hours after the study drug administration. Dense PDS and plasma sampling was performed for 24 hours after the start of administration. PK parameters were analysed with population PK modelling. Probability of target attainment (PTA) was simulated for different CAZ/AVI doses. RESULTS: PK profiles of both drugs in plasma and PDS were similar, indicating that the two drugs are well suited for a fixed-dose combination. A two-compartment model best described the PK of both drugs. A single dose of 2 g/0.5 g CAZ/AVI led to concentrations that far exceeded the PK/PD targets of both drugs. In the Monte Carlo simulations, even the lowest dose (750/190 mg CAZ/AVI) achieved a PTA of >90% for MICs up to 8 mg/L (The European Committee on Antimicrobial Susceptibility Testing epidemiological cut-off value for Pseudomonas aeruginosa) in plasma and PDS. DISCUSSION: On the basis of PTA simulations, a dose of 750/190 mg CAZ/AVI would be sufficient to treat plasma and peritoneal fluid infections in patients undergoing APD.

Cangrelor in Patients With Coronary Artery Disease Pretreated With Ticagrelor: The Switching Antiplatelet (SWAP)-5 Study.

BACKGROUND: There are no studies specifically designed to rule out a drug-drug interaction (DDI) when cangrelor is used among patients who have been pretreated with ticagrelor. OBJECTIVES: This study sought to rule out a DDI among cangrelor-treated patients who have been pretreated with ticagrelor. METHODS: In this prospective, randomized, double-blind, placebo-controlled, crossover, pharmacokinetic (PK) and pharmacodynamic (PD) study, patients with coronary artery disease (N = 20) were pretreated with a 180-mg ticagrelor loading dose and after 1 hour randomized to placebo or cangrelor (bolus and infusion for 2 hours). Patients crossed over after 1 to 4 weeks of washout. PK analysis included ticagrelor plasma levels and its active metabolite. PD assessments included VerifyNow P2Y12 reaction units (PRU), light transmittance aggregometry, vasodilator-stimulated phosphoprotein, and Total Thrombus-Formation Analysis System. PK/PD assessments were performed at 7 time points. RESULTS: Compared with placebo, adding cangrelor to patients pretreated with ticagrelor resulted in a significant reduction in PRU at 30 minutes and 1 hour after starting infusion. At 2 hours after stopping cangrelor/placebo infusion, PRU were low and similar in both groups (16.9 vs 12.6; mean difference: 4.3; 95% CI: -28.6 to 37.3), meeting the noninferiority primary endpoint (predefined noninferiority margin 45 PRU). Consistent findings were shown with all PD assays. PK tracked PD findings with no differences between groups in plasma levels of ticagrelor and its metabolite. CONCLUSIONS: Compared with placebo, the use of cangrelor in patients pretreated with ticagrelor results in enhanced platelet inhibition with no differences in PK/PD profiles after discontinuation of drug infusion indicating the absence of a DDI. (PD and PK Profiles of Switching Between Cangrelor and Ticagrelor Following Ticagrelor Pre-treatment [SWAP-5]; NCT04634162).

A multi-omics based anti-inflammatory immune signature characterizes long COVID-19 syndrome.

To investigate long COVID-19 syndrome (LCS) pathophysiology, we performed an exploratory study with blood plasma derived from three groups: 1) healthy vaccinated individuals without SARS-CoV-2 exposure; 2) asymptomatic recovered patients at least three months after SARS-CoV-2 infection and; 3) symptomatic patients at least 3 months after SARS-CoV-2 infection with chronic fatigue syndrome or similar symptoms, here designated as patients with long COVID-19 syndrome (LCS). Multiplex cytokine profiling indicated slightly elevated pro-inflammatory cytokine levels in recovered individuals in contrast to patients with LCS. Plasma proteomics demonstrated low levels of acute phase proteins and macrophage-derived secreted proteins in LCS. High levels of anti-inflammatory oxylipins including omega-3 fatty acids in LCS were detected by eicosadomics, whereas targeted metabolic profiling indicated high levels of anti-inflammatory osmolytes taurine and hypaphorine, but low amino acid and triglyceride levels and deregulated acylcarnitines. A model considering alternatively polarized macrophages as a major contributor to these molecular alterations is presented.

Simvastatin therapy in higher dosages deteriorates bone quality: Consistent evidence from population-wide patient data and interventional mouse studies.

BACKGROUND: Combining mouse experiments with big data analysis of the Austrian population, we investigated the association between high-dose statin treatment and bone quality. METHODS: The bone microarchitecture of the femur and vertebral body L4 was measured in male and ovariectomized female mice on a high-fat diet containing simvastatin (1.2 g/kg). A sex-specific matched big data analysis of Austrian health insurance claims using multiple logistic regression models was conducted (simvastatin 60-80 mg/day vs. controls; males: n = 138,666; females: n = 155,055). RESULTS: High-dose simvastatin impaired bone quality in male and ovariectomized mice. In the trabecular femur, simvastatin reduced bone volume (µm3: ♂, 213 ± 15 vs. 131 ± 7, p < 0.0001; ♀, 66 ± 7 vs. 44 ± 5, p = 0.02) and trabecular number (1/mm: ♂, 1.88 ± 0.09 vs. 1.27 ± 0.06, p < 0.0001; ♀, 0.60 ± 0.05 vs. 0.43 ± 0.04, p = 0.01). In the cortical femur, bone volume (mm3: ♂, 1.44 ± 0.03 vs. 1.34 ± 0.03, p = 0.009; ♀, 1.33 ± 0.03 vs. 1.12 ± 0.03, p = 0.0002) and cortical thickness were impaired (µm: ♂, 211 ± 4 vs. 189 ± 4, p = 0.0004; ♀, 193 ± 3 vs. 169 ± 3, p < 0.0001). Similar impairments were found in vertebral body L4. Simvastatin-induced changes in weight or glucose metabolism were excluded as mediators of deteriorations in bone quality. Results from mice were supported by a matched cohort analysis showing an association between high-dose simvastatin and increased risk of osteoporosis in patients (♂, OR: 5.91, CI: 3.17-10.99, p < 0.001; ♀, OR: 4.16, CI: 2.92-5.92, p < 0.001). CONCLUSION: High-dose simvastatin dramatically reduces bone quality in obese male and ovariectomized female mice, suggesting that direct drug action accounts for the association between high dosage and increased risk of osteoporosis as observed in comparable human cohorts. The underlying pathophysiological mechanisms behind this relationship are presently unknown and require further investigation.

Comparison of pharmacokinetics and stability of generics of cefepime, linezolid and piperacillin/tazobactam with their respective originator drugs: an intravenous bioequivalence study in healthy volunteers.

OBJECTIVES: The efficacy and quality of generic antibacterial drug formulations are often questioned by both healthcare specialists and patients. Therefore, the present study investigated the interchangeability of generic drugs with their originators by comparing bioequivalence parameters and stability data of generic cefepime, linezolid and piperacillin/tazobactam with their respective originator drugs. METHODS: In this open-label, randomized, crossover bioequivalence study, three groups of 12 healthy volunteers each received a single intravenous infusion of either 2 g of cefepime or 4.5 g of piperacillin/tazobactam and two generic formulations, or 600 mg of linezolid and one generic formulation. Plasma sampling was performed, with a 5 day washout period between study days. Stability was tested by storing reconstituted generic and originator products according to their own storage specifications and those of the comparator products. All concentrations were measured by LC-MS. RESULTS: Similar ratios of generic/originator (90% CI) Cmax were observed for Cefepime-MIP/Maxipime [93.7 (88.4-99.4)], Cefepime Sandoz/Maxipime [95.9 (89.1-103.2)], Linezolid Kabi/Zyvoxid [104.5 (91.1-119.9)], Piperacillin Kabi/Tazobac [95.9 (90.4-101.7)], Piperacillin Aurobindo/Tazobac [99.7 (84.9-104.7)], Tazobactam Kabi/Tazobac [93.4 (87.4-99.8)] and Tazobactam Aurobindo/Tazobac [97.4 (89.7-105.8)]. Accordingly, similar ratios of AUC0-t were observed for Cefepime-MIP/Maxipime [91.1 (87.6-94.8)], Cefepime Sandoz/Maxipime [97.9 (92.5-103.5)], Linezolid Kabi/Zyvoxid [99.7 (93.3-106.6)], Piperacillin Kabi/Tazobac [92.2 (88.3-96.3)], Piperacillin Aurobindo/Tazobac [99.9 (97.0-102.8)], Tazobactam Kabi/Tazobac [91.4 (86.4-96.7)] and Tazobactam Aurobindo/Tazobac [98.8 (94.3-103.6)]. Stable and similar concentrations were measured for all contiguous substances, regardless of storage conditions. CONCLUSIONS: Compared with their respective originator drugs, generic cefepime, linezolid and piperacillin/tazobactam met the predetermined bioequivalence criteria. All formulations were stable under the storage conditions of their respective comparators.

Microdosing as a Potential Tool to Enhance Clinical Development of Novel Antibiotics: A Tissue and Plasma PK Feasibility Study with Ciprofloxacin.

BACKGROUND AND OBJECTIVE: In microdose studies, drug pharmacokinetics is measured in humans after administration of subtherapeutic doses. While previous microdose studies focused primarily on plasma pharmacokinetics, we set out to evaluate the feasibility of microdosing for a pharmacokinetic assessment in subcutaneous tissue and epithelial lining fluid. METHODS: Healthy subjects received a single intravenous bolus injection of a microdose of [14C]ciprofloxacin (1.1 µg, 7 kBq) with (cohort A, n = 9) or without (cohort B, n = 9) a prior intravenous infusion of a therapeutic dose of unlabeled ciprofloxacin (400 mg). Microdialysis and bronchoalveolar lavage were applied for determination of subcutaneous and intrapulmonary drug concentrations. Microdose [14C]ciprofloxacin was quantified by accelerator mass spectrometry and therapeutic-dose ciprofloxacin by liquid chromatography-tandem mass spectrometry. RESULTS: The pharmacokinetics of therapeutic-dose ciprofloxacin (cohort A) in plasma, subcutaneous tissue, and epithelial lining fluid was in accordance with previous data. In plasma and subcutaneous tissue, the dose-adjusted area under the concentration-time curve of microdose ciprofloxacin was similar in cohorts A and B and within an 0.8-fold to 1.1-fold range of the area under the concentration-time curve of therapeutic-dose ciprofloxacin. Penetration of microdose ciprofloxacin into subcutaneous tissue was similar in cohorts A and B and comparable to that of therapeutic-dose ciprofloxacin with subcutaneous tissue-to-plasma area under the concentration-time curve ratios of 0.44, 0.44, and 0.38, respectively. Penetration of microdose ciprofloxacin into epithelial lining fluid was highly variable and failed to predict the epithelial lining fluid penetration of therapeutic-dose ciprofloxacin. CONCLUSIONS: Our study confirms the feasibility of microdosing for pharmacokinetic measurements in plasma and subcutaneous tissue. Microdosing combined with microdialysis is a potentially useful tool in clinical antimicrobial drug development, but its applicability for the assessment of pulmonary pharmacokinetics with bronchoalveolar lavage requires further studies. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov NCT03177720 (registered 6 June, 2017).

Targeted temperature management after cardiac arrest is associated with reduced metabolism of pantoprazole - A probe drug of CYP2C19 metabolism.

OBJECTIVE: Targeted temperature management (TTM) is part of standard post-resuscitation care. TTM may downregulate cytochrome enzyme activity and thus impact drug metabolism. This study compared the pharmacokinetics (PK) of pantoprazole, a probe drug of CYP2C19-dependent metabolism, at different stages of TTM following cardiac arrest. METHODS: This prospective controlled study was performed at the Medical University of Vienna and enrolled 16 patients following cardiac arrest. The patients completed up to three study periods (each lasting 24 h) in which plasma concentrations of pantoprazole were quantified: (P1) hypothermia (33 °C) after admission, (P2) normothermia after rewarming (36 °C, intensive care), and (P3) normothermia during recovery (normal ward, control group). PK was analysed using non-compartmental analysis and nonlinear mixed-effects modelling. RESULTS: 16 patients completed periods P1 and P2; ten completed P3. The median half-life of pantoprazole was 2.4 h (quartiles: 1.8-4.8 h) in P1, 2.8 h (2.1-6.8 h, p = 0.046 vs. P1, p = 0.005 vs. P3) in P2 and 1.2 h (0.9 - 2.3 h, p = 0.007 vs. P1) in P3. A two-compartment model described the PK data best. Typical values for clearance were estimated separately for each study period, indicating 40% and 29% reductions during P1 and P2, respectively, compared to P3. The central volume of distribution was estimated separately for P2, indicating a 64% increase compared to P1 and P3. CONCLUSION: CYP2C19-dependent drug metabolism is downregulated during TTM following cardiac arrest. These results may influence drug choice and dosing of similarly metabolized drugs and may be helpful for designing studies in similar clinical situations.

Anti-interleukin-6 antibody clazakizumab in late antibody-mediated kidney transplant rejection: effect on cytochrome P450 drug metabolism.

Targeting interleukin-6 (IL-6) is a promising strategy to counteract antibody-mediated rejection (ABMR). In inflammatory states, IL-6 antagonism was shown to modulate cytochrome P450 (CYP), but its impact on drug metabolism in ABMR treatment was not addressed so far. We report a sub-study of a phase 2 trial of anti-IL-6 antibody clazakizumab in late ABMR (ClinicalTrials.gov, NCT03444103). Twenty kidney transplant recipients were randomized to clazakizumab versus placebo (4-weekly doses; 12 weeks), followed by a 9-month extension where all recipients received clazakizumab. To study CYP2C19/CYP3A4 metabolism, we administered pantoprazole (20 mg intravenously) at prespecified time points. Dose-adjusted C0 levels (C0 /D ratio) of tacrolimus (n = 13) and cyclosporin A (CyA, n = 6) were monitored at 4-weekly intervals. IL-6 and C-reactive protein were not elevated at baseline, the latter was then suppressed to undetectable levels under clazakizumab. IL-6 blockade had no clinically meaningful impact on pantoprazole pharmacokinetics (area under the curve; baseline versus week 52: 3.16 [2.21-7.84] versus 4.22 [1.99-8.18] µg/ml*h, P = 0.36) or calcineurin inhibitor C0 /D ratios (tacrolimus: 1.49 [1.17-3.20] versus 1.37 [0.98-2.42] ng/ml/mg, P = 0.21; CyA: 0.69 [0.57-0.85] versus 1.08 [0.52-1.38] ng/ml/mg, P = 0.47). We conclude that IL-6 blockade in ABMR - in absence of systemic inflammation - may have no meaningful effect on CYP metabolism.

Effect of Ketamine on Human Neurochemistry in Posterior Cingulate Cortex: A Pilot Magnetic Resonance Spectroscopy Study at 3 Tesla.

Ketamine is a powerful glutamatergic long-lasting antidepressant, efficient in intractable major depression. Whereas ketamine's immediate psychomimetic side-effects were linked to glutamate changes, proton MRS (1H-MRS) showed an association between the ratio of glutamate and glutamine and delayed antidepressant effect emerging ∼2 h after ketamine administration. While most 1H-MRS studies focused on anterior cingulate, recent functional MRI connectivity studies revealed an association between ketamine's antidepressant effect and disturbed connectivity patterns to the posterior cingulate cortex (PCC), and related PCC dysfunction to rumination and memory impairment involved in depressive pathophysiology. The current study utilized the state-of-the-art single-voxel 3T sLASER 1H-MRS methodology optimized for reproducible measurements. Ketamine's effects on neurochemicals were assessed before and ∼3 h after intravenous ketamine challenge in PCC. Concentrations of 11 neurochemicals, including glutamate (CRLB ∼ 4%) and glutamine (CRLB ∼ 13%), were reliably quantified with the LCModel in 12 healthy young men with between-session coefficients of variation (SD/mean) <8%. Also, ratios of glutamate/glutamine and glutamate/aspartate were assessed as markers of synaptic function and activated glucose metabolism, respectively. Pairwise comparison of metabolite profiles at baseline and 193 ± 4 min after ketamine challenge yielded no differences. Minimal detectable concentration differences estimated with post hoc power analysis (power = 80%, alpha = 0.05) were below 0.5 µmol/g, namely 0.39 µmol/g (∼4%) for glutamate, 0.28 µmol/g (∼10%) for Gln, ∼14% for glutamate/glutamine and ∼8% for glutamate/aspartate. Despite the high sensitivity to detect between-session differences in glutamate and glutamine concentrations, our study did not detect delayed glutamatergic responses to subanesthetic ketamine doses in PCC.

The effect of oral Δ-9-tetrahydrocannabinol on the minimal alveolar concentration of sevoflurane: A randomised, controlled, observer-blinded experimental study.

BACKGROUND: Cannabis has increasingly been used for medical and recreational purposes. The main pharmacological compound in cannabis is tetrahydrocannabinol (THC), which has sedative, anxiolytic and analgesic effects. In some animal models, THC has also been shown to reduce the minimum alveolar concentration (MAC) of halothane and cyclopropane, but its effect on sevoflurane, currently the most commonly used inhalational anaesthetic agent, has not been investigated. OBJECTIVE: To investigate the effect of THC on the MAC of sevoflurane in rats. METHODS: Observer-blinded, randomised controlled trial. SETTING: Centre for Biomedical Research of the Medical University of Vienna, 2019. INDIVIDUALS: Thirty-eight adult Wistar rats. INTERVENTIONS: The rats were allocated randomly into one of two groups. Group A received THC 10 mg kg and group B received the corresponding volume of placebo via gastric gavage (administration through a tube placed in the distal oesophagus). The rats were then individually anaesthetised in an airtight sevoflurane-flooded chamber, and the MAC in both groups was determined using Dixon's up-and-down method. Blood samples were drawn to measure serum concentrations of THC. MAIN OUTCOME MEASURES: The primary outcome was the MAC of sevoflurane in Groups A and B. RESULTS: The bootstrap estimate of the MAC of sevoflurane was 2.1 (95% confidence interval 1.8 to 2.4) vol% in the THC group and 2.8 (95% confidence interval 2.7 to 2.9) vol% in the placebo group, corresponding to a significant MAC reduction of 26% in response to THC. CONCLUSION: Gastric administration of THC 10 mg kg significantly reduced the MAC of sevoflurane by 26%. TRIAL REGISTRATION: Not applicable.

Effect of Ketamine on Limbic GABA and Glutamate: A Human In Vivo Multivoxel Magnetic Resonance Spectroscopy Study.

INTRODUCTION: Converging evidence suggests that ketamine elicits antidepressant effects via enhanced neuroplasticity precipitated by a surge of glutamate and modulation of GABA. Magnetic resonance spectroscopic imaging (MRSI) illustrates changes to cerebral glutamate and GABA immediately following ketamine administration during dissociation. However, few studies assess subacute changes in the first hours following application, when ketamine's antidepressant effects emerge. Moreover, ketamine metabolites implicated in its antidepressant effects develop during this timeframe. Thus, this study aimed to investigate subacute changes in cerebral Glx (glutamate + glutamine), GABA and their ratio in seven brain regions central to depressive pathophysiology and treatment. METHODS: Twenty-five healthy subjects underwent two multivoxel MRS scans using a spiral encoded, MEGA-edited LASER-localized 3D-MRSI sequence, at baseline and 2 h following intravenous administration of racemic ketamine (0.8 mg/kg bodyweight over 50 min). Ketamine, norketamine and dehydronorketamine plasma levels were determined at routine intervals during and after infusion. Automated region-of-interest (ROI)-based quantification of mean metabolite concentration was used to assess changes in GABA+/total creatine (tCr), Glx/tCr, and GABA+/Glx ratios in the thalamus, hippocampus, insula, putamen, rostral anterior cingulate cortex (ACC), caudal ACC, and posterior cingulate cortex. Effects of ketamine on neurotransmitter levels and association with ketamine- and metabolite plasma levels were tested with repeated measures analyses of variance (rmANOVA) and correlation analyses, respectively. RESULTS: For GABA+/tCr rmANOVA revealed a measurement by region interaction effect (puncorr < 0.001) and post hoc pairwise comparisons showed a reduction in hippocampal GABA+/tCr after ketamine (pcorr = 0.02). For Glx/tCr and GABA+/Glx neither main effects of measurement nor measurement by region interactions were observed (all puncorr > 0.05). Furthermore, no statistically significant associations between changes in any of the neurotransmitter ratios and plasma levels of ketamine, norketamine, or dehydronorketamine were observed (pcorr > 0.05). CONCLUSION: This study provides evidence for decreased hippocampal GABA+/tCr ratio 2 h following ketamine administration. As MRS methodology measures total levels of intra- and extracellular GABA, results might indicate drug induced alterations in GABA turnover. Our study in healthy humans suggests that changes in GABA levels, particularly in the hippocampus, should be further assessed for their relevance to ketamine´s antidepressant effects.

Low pH reduces the activity of ceftolozane/tazobactam in human urine, but confirms current breakpoints for urinary tract infections.

BACKGROUND: Acidic pH has been shown to impact the antibiotic activity of non-ß-lactams in urine. OBJECTIVES: To investigate the in vitro activity of ceftolozane/tazobactam compared with meropenem at different pH settings in urine. METHODS: We determined the MICs for 30 clinical isolates of Escherichia coli, 25 clinical isolates of Klebsiella pneumoniae and 24 clinical isolates of Proteus mirabilis in pooled human urine and standard growth medium at pH 5 and 7. Time-kill curves were produced for one representative clinical isolate of tested bacterial strains in urine at pH 5, 6 and 7 for both antibiotics at concentrations above and below the MIC. HPLC analysis of the stability of ceftolozane/tazobactam and meropenem was performed at different pH values. RESULTS: The median MICs of both antibiotics were up to 8-fold higher at pH 5 than at pH 7. Bacterial growth of E. coli was not impacted by pH, while for K. pneumoniae and P. mirabilis low pH slightly reduced growth. Compared with pH 7, pH 5 resulted in a significant decrease in antibiotic activity with a delta of up to 3 log10 bacterial counts after 24 h. Impact of acidic pH was lowest for P. mirabilis; however, this strain metabolically increased the pH during experiments. Stability was not impacted by low pH. CONCLUSIONS: Acidic pH had a significant negative impact on the activity of ceftolozane/tazobactam and meropenem in urine. Considering concentrations achieved in urine, our results confirm existing breakpoints and do not advocate increasing ceftolozane/tazobactam breakpoints for urinary tract infections.

Impact of thrombocytes, on bacterial growth and antimicrobial activity of selected antibiotics.

In vitro pharmacodynamic models are used to optimize in vivo dosing regimens in antimicrobial drug development. One limiting factor of such models is the lack of host factors such as corpuscular blood components as erythrocytes which have already been shown to impact activity of antibiotics and/or growth of the pathogen. However, the impact of thrombocytes has not previously been investigated. We set out to investigate if the addition of thrombocytes (set to physiological concentrations in blood of healthy human, i.e., 5 × 105 thrombocytes/µL standard growth media Mueller Hinton Broth, MHB) has an influence on bacterial growth and on the efficacy of antibiotics against Gram+ and Gram- bacteria. Growth assays and time-killing-curves (TKC) were performed with ATCC-strains of Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa in triplicate over 24 h. The same approach was followed for 5 clinical isolates of Escherichia coli. Meropenem, ciprofloxacin, and tigecycline were tested as representatives of broad-spectrum antibiotics, and concentrations several-fold above and below the minimal inhibitory concentration (MIC) were simulated. No significant impact of thrombocytes was found on bacterial growth or antimicrobial stability for the investigated agents. Bacteria reduced thrombocyte content to different degree, indicating direct interaction of pathogens and thrombocytes. Impact on bacterial killing was observed but was not fully reproducible when thrombocytes from different donors where used. While interaction of bacteria and thrombocytes was evident in the present study, interaction between antibiotic activity and thrombocytes seems unlikely. Whether variability was caused by different thrombocyte concentrates needs further investigation.

Gastric Emptying and Distal Gastrectomy Independently Enhance Postprandial Glucagon-Like Peptide-1 Release After a Mixed Meal and Improve Glycemic Control in Subjects Having Undergone Pancreaticoduodenectomy.

OBJECTIVES: New-onset diabetes frequently resolves after pancreaticoduodenectomy (PD). Glucagon-like peptide-1 (GLP-1) conceivably is involved as its release is enhanced by rapid gastric emptying and distal bowel exposure to nutrients. We aimed at studying factors associated with GLP-1 release after PD. METHODS: Fifteen PD subjects with distal gastrectomy (Whipple) and 15 with pylorus preservation were evaluated. A test meal containing 1 g paracetamol to measure gastric emptying was ingested. Blood for the measurement of paracetamol, glucose, insulin, and GLP-1 was drawn at baseline and 10, 20, 30, 60, 90, 120, 150, and 180 minutes thereafter. The Matsuda index of insulin sensitivity was calculated. RESULTS: In univariate analysis, gastric emptying correlated with GLP-1. Glucagon-like peptide-1 responses to the modes of operation did not differ. Multiple regression analysis confirmed gastric emptying and Whipple versus pylorus-preserving pancreaticoduodenectomy as independent predictors of GLP-1 release. The Matsuda index of insulin sensitivity correlated with GLP-1 concentrations and inversely with body mass index. Patients after Whipple procedure revealed lower glycated hemoglobin as compared with pylorus-preserving pancreaticoduodenectomy. CONCLUSIONS: Following PD, the postprandial GLP-1 release seems to be enhanced by rapid gastric emptying and to improve insulin sensitivity. Partial gastrectomy versus pylorus preservation enhanced the release of GLP-1, conceivably because of greater distal bowel exposure to undigested nutrients.

Impact of erythrocytes on bacterial growth and antimicrobial activity of selected antibiotics.

It has been shown that protein binding, temperature, and pH influence in vitro pharmacodynamic (PD) models. The fact that corpuscular blood compounds might also have an important impact is something which has, until now, often been neglected. We investigated if the addition of human erythrocytes to standard growth media (Mueller Hinton Broth, MHBII) has an influence on bacterial growth behavior and on antibiotic efficacy. We did this by using bacterial growth assays and time kill curves (TKC) of selected strains (Escherichia coli ATCC25922, Staphylococcus aureus ATCC29213, and Pseudomonas aeruginosa ATCC27853) over 24 h. The final concentration of erythrocytes was set to match the physiological concentrations in the blood of a healthy human, i.e., 3 × 10^6 cells/µl in MHBII. Meropenem, ciprofloxacin, and tigecycline were tested with concentrations several-fold above and below the minimal inhibitory concentration (MIC). Moreover, HPLC analysis of antibiotic stability and distribution in erythrocytes was performed. Meropenem, ciprofloxacin, and tigecycline showed the greatest decline in activity against E. coli when erythrocytes were present. A mean difference in log10 bacterial killing between pure MHBII and 50%-Ery of 3.83, 1.33, and 2.42 was found for ciprofloxacin, meropenem, and tigecycline, respectively. In the case of ciprofloxacin, HPLC analysis revealed that less extracellular antibiotic is available in the presence of erythrocytes. We have demonstrated that erythrocytes do influence antimicrobial activity and that this might have an impact on the extrapolation of in vitro activity testing to in vivo efficacy in patients.

Evidence of human milk oligosaccharides in maternal circulation already during pregnancy: a pilot study.

Human milk oligosaccharides (HMOs) are bioactive glycans linked with health benefits to both the breast-fed infant and lactating mother. We hypothesized that HMOs are present before lactation, already during pregnancy, and are influenced by maternal body composition. In a pilot study, we investigated individual and temporal variations in HMO composition and concentration in maternal serum at gestational weeks 10-14 ( visit 1), 20-24 ( visit 2), and 30-35 (visit 3) (V1, V2, and V3, respectively) and associations with maternal body composition. HMOs were quantified by HPLC and confirmed by enzymatic digest and mass spectrometry. Associations of maternal prepregnancy body mass index (BMI), subcutaneous adipose tissue (SAT) thickness, and adipokines with absolute and relative HMO concentrations were analyzed by Spearman correlation. We identified 16 HMOs and 2 oligosaccharides not common to human milk. HMO concentration and composition varied with gestational age and secretor status. HMO concentration increased with gestational age and changed from a predominantly sialylated profile at V1 to a more balanced fucosylated-to-sialylated ratio at V3, mostly due to a profound increase in 2'-fucosyllactose (2'-FL), reflecting secretor phenotype. In secretor-positive women, BMI was negatively correlated with 2'-FL at V2. SAT at V1 and V2 were strongly negatively correlated with 2'-FL concentrations. This pilot study shows that prenatal HMOs are present in maternal serum, suggesting roles for HMOs already during pregnancy. Our result that maternal body composition is associated with prenatal HMOs might indicate that maternal metabolism modulates HMO composition with unknown implications for maternal and fetal health already during pregnancy.

Massive release of the histamine-degrading enzyme diamine oxidase during severe anaphylaxis in mastocytosis patients.

BACKGROUND: Histaminolytic activity mediated by diamine oxidase (DAO) is present in plasma after induction of severe anaphylaxis in rats, guinea pigs, and rabbits. Heparin released during mast cell degranulation in the gastrointestinal tract might liberate DAO from heparin-sensitive storage sites. DAO release during anaphylaxis has not been demonstrated in humans. METHODS: Plasma DAO, tryptase, and histamine concentrations of four severe anaphylaxis events were determined at multiple serial time points in two patients with systemic mastocytosis. The histamine degradation rates were measured in anaphylaxis samples and in pregnancy sera and plasma with comparable DAO concentrations. RESULTS: Mean DAO (132 ng/mL) and tryptase (304 ng/mL) concentrations increased 187- and 4.0-fold, respectively, over baseline values (DAO 0.7 ng/mL, tryptase 76 ng/mL) during severe anaphylaxis. Under non-anaphylaxis conditions, DAO concentrations were not elevated in 29 mastocytosis patients compared to healthy volunteers and there was no correlation between DAO and tryptase levels in mastocytosis patients. The histamine degradation rate of DAO in plasma from mastocytosis patients during anaphylaxis is severely compromised compared to DAO from pregnancy samples. CONCLUSION: During severe anaphylaxis in mastocytosis patients, DAO is likely released from heparin-sensitive gastrointestinal storage sites. The measured concentrations can degrade histamine, but DAO activity is compromised compared to pregnancy samples. For accurate histamine measurements during anaphylaxis, DAO inhibition is essential to inhibit further histamine degradation after blood withdrawal. Determination of DAO antigen levels might be of clinical value to improve the diagnosis of mast cell activation.